Category Archives: Gardening

Eliminate mosquitoes by eliminating stagnant water

The most effective, cheapest way to control mosquitoes is to eliminate the standing water that larvae need to develop. A dry yard doesn’t have mosquitoes. It’s really that simple. Below is a list of objects to get rid of or dump regularly. Please share with your neighbors.

1. Gutters

This is at the top of the list because almost all houses have gutters and almost all homeowners hate to clean them out. Check for blocked gutters weekly if you have a lot of trees nearby. If gutter status is hard to see, buy a drone to facilitate inspections. If you can’t afford a drone just get an extra-long, telescoping selfie stick for your smartphone.

2. Flexible downspout extenders

Flexible downspout extenders are perfect for mosquito larvae — the ridges hold water and the black absorbs heat from sunlight (thus speeding development). They are especially bad if nestled in shrubs and ground cover. Note that they hold water even if they are sloped downward. Get rid of them. All of them.

3. Tarps

If you leave a tarp in your yard, you’ve created lots of nooks in which water and debris will accumulate. I frequently see tarps covering soggy logs that owners seem to have no real intention of ever splitting into firewood. I think people view tarps as cloaks of invisibility, magically hiding loathsome to-do items from spouse.

4. Toys

Sandbox toys, sleds, wagons, and kiddie pools seem as if they were specifically designed to encourage mosquitoes. I.e., even when stored upside down they have nooks that collect enough rainwater to allow mosquito larvae to mature. Store them in the garage. If you think covering them with a tarp will work, please see #3.

5. Bird baths

Everyone should have a bird bath. But if you do, you need to either have a water bubbler/agitator (mosquitoes hate that) or you need to kill the larvae by adding granules of Bacillus thuringiensis var israelensis (abbreviated, Bti). Bti is extremely effective: you can add it a container that has thousands wriggling of larvae (see movie) and they will all be dead within hours. Just add it every two weeks and your bath will always be mosquito free. But don’t forget — make yourself a smartphone reminder or write on paper calendar.

Bird bath next to purple coneflowers

6. Trash and recycling bins

If you can’t store your trash and recycling containers under a roofed area, keep a lid on them. I found the ones below behind a local church. Tens of thousands of larvae within.

Recycling bins with stagnant water

7. Watering cans

Watering cans are rarely transparent so you can’t see the mosquito larvae inside, but they are present if you leave them around the yard when it’s been raining a lot. Store them empty, in garage.

8. Wheelbarrows

Just keep them propped up vertically so they don’t accumulate rain water. Or drill holes.

9. Rain barrels

Just put screening over the top. Or add Bti every other week. I don’t recommend adding mosquito-eating fish because they die when water level gets low (plus the fish suffer before dying).

10. Pot saucers

Pot saucers are unneeded outside so it’s easy to eliminate them. If you like them for decorative reasons you’ll need to add Bti regularly. It’s better to just get rid of them because you’ll eventually forget. You know you will.

Other places where mosquitoes larvae thrive

Other objects of concern are: pool covers, pot saucers, grill covers, plastic kid toys, tires, unattached hoses, empty glazed pots, shovels, construction materials, garbage cans, garbage can lids, containers in recycling bins, bottle caps, cemetery vases, decorative shells, empty coconuts, papaya tree stumps, downspout troughs, spigot drips, ollas, pickup truck beds, window wells, septic tanks, uncapped metal fence posts, animal tracks. Mosquitoes will also lay eggs inside in toilet bowls, animal water dishes, and French drains.

Identifying mantid egg cases in Pennsylvania

Below are photographs and descriptions of egg cases of the (native) Carolina mantis, the European (=praying) mantis, the Chinese mantis, and the narrow-winged mantis.

Carolina mantid (Stagmomantis carolina)

Carolina mantids (the only native species in my area) form relatively smooth, teardrop-shaped oothecae with a central portion that is lightly colored. Often found on tree trunks, rocks, and buildings.

Egg case of Carolina mantid (Stagmomantis carolina)

European mantis (Mantis religiosa)

These oothecae are somewhat similar to the Carolina mantis’ but lack the alternating bands of color. Another common name for the European mantis is the praying mantis.

Egg case of European mantis (Mantis religiosa)

Chinese mantid (Tenodera sinensis)

Chinese mantid oothecae are typically roundish, roughly textured, and uniform in color. Introduced from Asia, as you probably guessed.

Egg case of Chinese mantid (Tenodera sinensis)

Narrow-winged mantid (Tenodera angustipennis)

Narrow-winged mantid oothecae are usually rather elongate. They are also seem to have red streaks, though the color seems to be most noticeable after they age a few months. Introduced from Asia, too.

Egg case of narrow-winged mantid (Tenodera angustipennis)

More ID help

For an excellent overview of all of these species, please see the Cape May Wildlife Guide’s page on mantids. Please also see the excellent guide by Paweł Pieluszyński of the Brooklyn Bridge Park, especially because it includes an ootheca of the Asian jumping mantis (Statilia maculata) that is probably lurking undiscovered in Pennsylvania. If you need help identifying an ootheca, I highly recommend posting a photograph on iNaturalist. Not only will you get an answer from the iNaturalist community within a day or two, your submission helps scientists track the spread of invasive species.

What should you do with the non-native oothecae?

Invasive mantids eat butterflies, native bees, honey bees, small birds, and also the native mantid, so when you find egg cases, dispose of them. Here are some suggestions on how to do that:

  • Put them in a freezer for a week
  • Step on them
  • Give them to a neighbor who has chickens
  • Give them to local bird rehabilitation centers
  • Give them to a neighbor who has a pet tarantula, snake, lizard, or fish

Whatever you do, please not just relocate oothecae to some nearby field — that just transfers the problem to someplace where you can’t see the problem.

But aren’t mantids great for pest control?

Although it’s true that young mantids consume a lot of insects, some of which might be pests, when mantids are fully grown they tend to camp out on flowers and wait for large butterflies and even small birds. Mantids are, of course, excellent for controlling butterflies and hummingbirds in case you happen to hate those animals.

Monarch butterfly captured by a Chinese mantid (Tenodera sinensi
Monarch butterfly captured by a Chinese mantid (Tenodera sinensis).